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Listeria cases rise sharply in Sweden as 94 sickened

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By Joe Whitworth+

Last updated on 02-Sep-2014 at 11:52 GMT

One of the outbreaks could be linked to cold meat products such as ham
One of the outbreaks could be linked to cold meat products such as ham

The Public Health Agency in Sweden is investigating two outbreaks of Listeria that have sickened at least 60 people.

A total of 94 cases of listeriosis have been reported until the middle of August, compared with 46 during the corresponding period last year, but these include cases with different strains than those involved in the outbreaks.

The agency (Folkhälsomyndigheten in Swedsh) is attempting to find the source after noting the increased cases in two sepeate outbreaks that started in May 2014 and October last year.

In May this year, the first case of a Listeria outbreak was reported.

So far, 14 people have fallen ill, mostly in the southern parts of the country. The source of infection is unknown, but the investigation is ongoing.

Skåne has noted six cases, Stockholm three, Östergötland two and Örebro, Gävleborg and Halland all one. People affected range in age from over 40 to over 90.

Outbreak investigation

Anders Wallensten, deputy state epidemiologist for the health agency, said the two outbreaks come from patterned clusters.

“Investigations are a collaboration between us and the National Food Agency,” he told

Different strains of Listeria are involved in the outbreaks

“They inspect the suspect premises, test samples of food and we gather information through interviews and find the link to a food item by comparing answers with healthy individuals.

“The first outbreak so far has been linked to cold cut meats and for the second outbreak we are not sure yet.

“It looks like an ongoing source as if it was just an incident you would have thought cases would stop but there might be still contamination in a food premises.”

Wallensten added that the cases are not linked to the outbreak in Denmark and they are using Pulsed Field Gel Electrophoresis (PFGE) and whole genome sequencing (WGS) in their work.  

October outbreak ongoing

An outbreak began in October last year where 44 people have been infected so far.

Analysis of survey responses indicate that various meat products such as liver pate, ham and salami may be the reason, but the source of infection is not yet fully understood.

The cases were reported mainly from the southern and central parts of the country. People affected range in age from over 20 to over 90.

Cases have been reported in Skåne (14), Västra Götaland (7), Örebro (5) and Stockholm (3).

The Public Health Agency intensified surveillance of listeriosis in 2013, which has contributed to the outbreaks have been detected.

The investigations are carried out with the National Food Agency (Livsmedelsverket in Swedish) and the country's disease control units.

The Public Health Agency of Sweden said that Listeria outbreaks are difficult to investigate.

There is an average of three weeks between consuming the product and illness and many have difficulty remembering what they have eaten, it added.

Meanwhile, the Statens Serum Institut (SSI) in Denmark has updated the case count to reveal 34 illnesses (19 women and 15 men) with the related deaths remaining at 13. 

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